Do a vent check ...
https://www.backyardchickens.com/articles/who-is-laying-and-who-is-not-butt-check.73309/
I suspect the BO, Australorp and/or Wyandotte ; look at the color (redness of their combs and wattles ... Anyone squatting when you get close? Australops & Wyandottes I had usually did...